We humans breathe in oxygen—you probably knew this—and we breathe out carbon dioxide. In an enclosed space, it’s possible for carbon dioxide to build up in the air. Some research shows that meeting rooms and classrooms may be enclosed enough to reach mind-numbing carbon dioxide concentrations.
If you live in a large city with traffic and cars, you’re likely exposed to air pollution on a daily basis. That can have detrimental effects on your health, especially your lungs, and the surgical masks you often see in smoggy cities actually don’t do a ton to protect you….